Graphitic Carbon Nitride-Based Microrobots: Progress and Prospects in Environmental and Biomedical Applications

Graphitic carbon nitride (g-C₃N₄) is a metal-free semiconductor responsive to visible light that has attracted considerable interest as a photocatalyst in environmental and biomedical applications. Constructing photocatalysts as light-driven microrobots allows simultaneous propulsion and catalytic activity, both driven by photoinduced charge separation. In addition, light-driven systems can perform remote control of micro/nanorobots (MNRs) and reduce their reliance on external chemical fuels. Thus, g-C₃N₄ has been investigated as a functional material for microrobots, owing to its low cost, chemical stability, and biocompatibility. This review presents an overview of g-C₃N₄-based microrobots, including their fabrication strategies for different morphologies, such as tubular, sheet-like, and spherical structures. It also discusses their propulsion mechanisms, including self-diffusiophoresis, self-electrophoresis, and bubble propulsion. Their applications in water purification, including the degradation of organic pollutants and the removal of heavy metals, are discussed, followed by biomedical uses such as antibacterial therapy and drug delivery. Finally, current challenges and prospects for the development of efficient and sustainable g-C₃N₄-based microrobots are outlined.